I was wondering what material in algebraic geometry is crucial and is a logical step for a serious graduate student in algebraic geometry once they've finished Hartshorne. Good answers could include a list of areas of algebraic geometry or important topics that an algebraic geometer must learn along with good references (i.e. accessible to someone with the background of Hartshorne), preferably in the order he or she should/could learn them. Papers in algebraic geometry tend to draw from so many areas within the field itself that I was wondering what people thought was the best order and way of acquiring that material.

One difficulty with this question is that the answers, taken together, are inevitably going to give far more (good) suggestions than one person could reasonably go through during a single graduate student career.
–
Charles StaatsApr 13 '11 at 20:19

11 Answers
11

Every algebraic geometer needs to know at least the basics of intersection theory.
Fulton's book is the standard reference and serves both as a textbook and a reference.

'Principles of Algebraic Geometry' by Griffiths and Harris

This is because Hartshorne does not really talk about complex geometry, Hodge theory or more classical algebraic geometry. It might also be good to see the classical approach to the theory developed in chapters 4 and 5 in Hartshorne which of course existed way before sheaf cohomology and schemes.

EGA by Grothendieck and Dieudonné.

This is if you want more of the Hartshorne style algebraic geometry. I would not say it is essential to read the entire EGA, but since it is the standard reference, it is at least worth getting to know it.

After Hartshorne, you could start specializing. Find something that seems interesting to you - you'll pick up a lot of new algebraic geometry even though you are studying a specific subtopic. After finishing Hartshorne's book you should be able to read these books without too much trouble.

Dear anonymous, Mumford wrote a short bookLectures on Curves on an Algebraic Surface which, according to the preface, was written for the reader you have in mind (although at the time Hartshorne's book didn't exist yet). The book corresponds to oral lectures and the sections ( called Lecture $n$) are essentially the notes that had been distributed in class after the lectures, which makes for easy to digest little units.

The book contains the construction of the Picard scheme of a surface and the Hilbert scheme of curves on that surface. Lectures 3 to 10 (out of 27) are recollections of the general theory of schemes, with very interesting insights on the functor of points aspect. For example Mumford describes
$\mathbb P^n(S)$ in terms of invertible sheaves on the scheme $S$ and their sections, he explains how to describe the Zariski tangent space of a functor defined on schemes even if the functor is not representable, etc.

The actual goal of the booklet is to prove a theorem of completeness of a characteristic linear system on a surface. The theorem was proved in characteristic zero analytically by Poincaré in 1910 but algebraically in all characteristics only in the 1960's by Grothendieck through systematic use of nilpotent elements. But as in all good books, the road is at least as interesting as the final destination, and much can be learned even if the book is not read to the end.

Lazarsfeld's book ``Positivity in Algebraic geometry'' contains a wealth of important material and is masterfully written. Anyone doing algebraic geometry today will greatly benefit from being familiar with the contents of this book.

Edit: here is a blog post by Burt Totaro on the importance of this topic/book:

Perhaps the first advice I could give is to ask your advisor or algebraic geometers at the university at which you are located, if you are a student, they might already have areas/problems in mind for you to work on and so can give you the best advice relative to those problems.

A couple books which have not yet been mentioned (some of which I wish I had gone through more carefully):

Higher-Dimensional Algebraic Geometry, by Olivier Debarre.

This is a nice somewhat more informal introduction that covers many of the topics in Kollar-Mori with I would say more examples. It also covers some of the material in "rational curves" .

Moduli of Curves, by Harris and Morrison

A standard introduction / reference on the topic (which is again heavily studied).

Rational curves on algebraic varieties, by János Kollár.

The study of algebraic varieties by studying their rational curves is a major area of investigation in algebraic geometry. This book is fairly technical but contains a lot of information.

Mumford's three part series Tata Lectures on Theta is well worth reading. (I wish I had read them already...I could sure use the information they contain.)

Added: Or really, close your eyes and pick a book by Fulton, Hartshorne, Kollar, Mumford, Silverman....If you get the book by Hartshorne that you've already read, pick again. Otherwise, whatever you picked will be a fine choice.

Yes, very nice. Especially nice if you want to learn about Neron models of course -- but seriously, the exposition is of such uniformly high quality that I it is an excellent reference even for things not (directly) related to the somewhat technical topic of its title.
–
Pete L. ClarkApr 14 '11 at 1:37

1

P.S.: Were it not for modesty issues, Neron-Raynaud models would arguably be a better title.
–
Pete L. ClarkApr 14 '11 at 1:37

I'm far from having read all of Hartshorne, but if I did I would study Compact Complex Surfaces, by Barth, Peters, Van de Ven. Also Geometric Invariant Theory would be a nice topic (I know about the book by Mumford, are there other good books on this topic?).

Ah, I forgot! How about derived categories? Someone suggested that for this topic a good reference is the book by Hartshorne Residues and duality. I had a look at some notes by Caldararu on the arxiv, "Derived categories of sheaves: a skimming", they seem well written.

I'm not familiar with he book by Bart, et. al., but if you're interested in Compact Complex Surfaces, then the book by Beauville it's quite excellent. He covers the Enriques classification in a very down-to-earth nice way, given that one has the tools from Hartshorne.
–
anonymousApr 13 '11 at 9:36

1

For GIT, there is also Dolgachev's "Lectures on Invariant theory."
–
Phillip WilliamsApr 13 '11 at 16:00

4

For derived categories, there is a nice book by Huybrechts called Fourier-Mukai Transforms in Algebraic Geometry.
–
Chuck HagueApr 13 '11 at 16:23

The basic idea common to all these suggestions is to use the foundational material from Hartshorne to investigate some more specialized topics, like curves, surfaces, abelian varieties, moduli spaces, singularities, or some more general techniques like intersection theory with applications to general Riemann Roch theorems, and vanishing theorems with applications to classification questions, plus arithmetic and analytic questions.